1. Field of the Invention (Technical Field)
The present invention relates to automated domain reflectometry testing of electrical components.
2. Background Art
Note that the following discussion refers to publications that due to recent publication/filing dates are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
The complexity of electronic components, particularly printed circuit boards, is steadily increasing, as is the demand for electronic components. These components need to be tested for faults, and high frequency signal techniques such as domain reflectometry provides an excellent technique for much of such testing. Because of the high volume of needed testing, automated robotic systems are preferred in order to attain a high throughput for any testing system.
Unfortunately, existing domain reflectometry robotic testing systems suffer from noise introduced by certain sources of imprecision in the systems themselves. For example, U.S. Pat. No. 5,994,909, to Lucas et al., discloses a robotic testing system having two probes 122, 123 mounted on a single robotic arm wherein probe 123 is adjustable so that the distance between the two probes is adjustable. Such a mechanical system is prone to imprecision over time, because of vibration, temperature fluctuations, and like sources of distortion. Similarly, European Patent Application EP 0 953 844 A2 (corresponding to U.S. Pat. No. 6,051,978, to Swart) discloses a two-probe system but having a single probe on each of two robotic arms. Again, maintaining a precise desired distance between the two probes is difficult, again resulting is unwanted distortion of the testing results. Because of such imprecisions in existing systems, the shortest traces that can be tested accurately are those that are 1.5 inches or longer.
The present invention greatly reduces noise by using a single robotic arm that employs twin probes (signal and ground) having a non-adjustable fixed distance (pitch) between them. Because testing often requires a number of different pitches, the robotic arm of the invention is able to select any of a plurality of fixed-pitch probes stored in a probe tip changer assembly. Because this prevents inaccuracies induced by changes in pitch over time plaguing prior art mechanical systems, the present invention is able to successfully test traces as short as 0.5 inches (and at least as long as 150 feet). The shapes of the probe tips and the preferred rectangular shape of the probe tip assembly contribute to accuracy by precisely mimicking the electrical characteristics of coaxial structures. A quick electrical disconnect device permits rapid engagement and disengagement of the probe assemblies from the robotic arm, contributing to rapid throughput. The present invention has a number of other advantages over the prior art as discussed below.
The following references also disclose robotic testing systems having varying advantages and disadvantages: U.S. Pat. No. 6,008,636, to Miller et al.; U.S. Pat. No. 5,781,021, to IIani; U.S. Pat. No. 5,498,965, to Mellitz; U.S. Pat. No. 6,024,526, to Slocum et al.; U.S. Pat. No. 5,844,412, to Norton; U.S. Pat. No. 5,696,450, to Itoh; U.S. Pat. No. 5,498,964, to Kerschner et al.; U.S. Pat. No. 5,469,064, to Kerschner et al.; U.S. Pat. No. 5,105,147, to Karasikov et al.; U.S. Pat. No. 4,881,863, to Braginsky; U.S. Pat. No. 5,631,856, to Keller et al.; U.S. Pat. No. 5,394,348, to Abe; U.S. Pat. No. 5,043,910, to Chiba; U.S. Pat. No. 4,628,464, to McConnell; and U.S. Pat. No. 4,593,820, to Antonie et al.
The present invention is of a automated domain reflectometry test system (and corresponding method) comprising: domain reflectometry instrumentation; a robotic arm; and a passive, high frequency probe assembly comprising a signal probe and a ground probe having a fixed, non-adjustable pitch, the probe assembly being electrically connected to the domain reflectometry instrumentation, and being moved, electrically connected to, and retracted from test points on an electrical component to be tested by the robotic arm. In an embodiment, the system additionally comprises a second robotic arm and a second passive, high frequency probe assembly having a fixed, non-adjustable pitch and being electrically connected to the domain reflectometry instrumentation, and being moved, electrically connected to, and retracted from test points on the electrical component to be tested by the second robotic arm, whereby differential domain reflectometry tests may be performed on the electrical component. In another embodiment, differential domain reflectometry tests can be performed with the probe assembly comprising a second signal probe and a second ground probe having a fixed, non-adjustable pitch. In the preferred embodiment, the system employs a probe assembly changing station accessible by the robotic arm, the probe assembly changing station comprising holders for a plurality of probe assemblies, together with a robotic control system that directs the robotic arm to acquire from the probe assembly changing station a probe assembly having a correct pitch for testing of test points of the electrical component having a same pitch. A calibration/verification station accessible by the robotic arm is preferably employed that comprises a calibrated airline. The system can test traces having a length of between approximately 0.5 inches and 150 feet such that a standard deviation of domain reflectometry test result impedances is 0.03 ohms or less. The probe assembly mimics electrical characteristics of a coaxial structure. The system can test components comprising dimensions of between approximately 5.25 inchesxc3x970.5 inches and 36 inchesxc3x9728.5 inches. The robotic control system comprises software for automatically planning testing of the electrical component by importation of computer aided design data for the electrical component. The system records impedance and propagation delay and calculates a dielectric constant for each test point of the electrical component.
The invention is also of a probe assembly changing station for a robotic domain reflectometry test system (and method), which changing station is accessible by a robotic arm of the system, the probe assembly changing station comprising holders for a plurality of passive, high frequency probe assemblies affixable to an end of the robotic arm and from which the robotic arm can without human intervention affix any of the plurality of probe assemblies. In the preferred embodiment, each of the probe assemblies comprises a passive, high frequency probe assembly comprising a signal probe and a ground probe having a fixed, non-adjustable pitch.
The invention is additionally of a robotic domain reflectometry test system (and corresponding method) comprising: differential domain reflectometry instrumentation; at least one robotic arm; and two passive, high frequency probe assemblies each comprising a signal probe, each the probe assembly being electrically connected to the differential domain reflectometry instrumentation, and being moved, electrically connected to, and retracted from test points on an electrical component to be tested by the at least one robotic arm. In one embodiment, the at least one robotic arm comprises a single robotic arm holding both the probe assemblies. In another embodiment, the at least one robotic arm comprises two robotic arms each holding one of the probe assemblies. In one embodiment, at least one of the probe assemblies additionally comprises a ground probe having a fixed, non-adjustable pitch with respect to the signal probe on the at least one of the probe assemblies. In another embodiment, both of the probe assemblies additionally comprise a ground probe having a fixed, non-adjustable pitch.
The invention is further of a robotic domain reflectometry test system (and corresponding method) comprising: domain reflectometry instrumentation; a robotic arm; a passive, high frequency probe assembly comprising a signal probe and a ground probe, the probe assembly being electrically connected to the domain reflectometry instrumentation, and being moved, electrically connected to, and retracted from test points on an electrical component to be tested by the robotic arm; and components recording impedance and propagation delay for each test of the test points and calculating and recording a dielectric constant for each test of the test points.
The invention is also of a robotic domain reflectometry test system (and corresponding method) comprising: domain reflectometry instrumentation; a robotic arm; and a passive, high frequency probe assembly comprising a signal probe and a ground probe, the probe assembly being electrically connected to the domain reflectometry instrumentation, and being moved, electrically connected to, and retracted from test points on an electrical component to be tested by the robotic arm; and wherein the system can test traces having a length of between approximately 0.5 inches and 150 feet such that a standard deviation of domain reflectometry test result impedances is 0.03 ohms or less.
The invention is additionally of a robotic domain reflectometry test system (and corresponding method) comprising: domain reflectometry instrumentation; a robotic arm; a passive, high frequency probe assembly comprising a signal probe and a ground probe, the probe assembly being electrically connected to the domain reflectometry instrumentation, and being moved, electrically connected to, and retracted from test points on an electrical component to be tested by the robotic arm; and a calibration/verification station accessible by the robotic arm and comprising a calibrated airline. In the preferred embodiment, the calibrated airline is a 28 ohm or 50 ohm NIST calibrated airline.
A primary object of the present invention is to provide a robotic domain reflectometry system with high accuracy.
Another object of the present invention is to provide a system that can move from test point to test point rapidly.
A primary advantage of the present invention is that it can provide accurate and repeatable domain reflectometry tests of traces of length between 0.5 inches and 150 feet (or more).
Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.